Process for producing artificial filaments



July 18, 1950 w. D. NICOLL PROCESS FOR PRODUCING ARTIFICIAL FILAMENTS 2 Sheets-Sheet 1 Filed Jan. 28, 1949 WilliafizDM'co-Zlmmvrox.

I ATTOZZ y 1950 w. D. NICOLL 2,515,889

PROCESS FOR PRODUCING ARTIFICIAL FILAMENTS Filed Jan. 28, 1949 2 Sheets-Sheet 2 Wl'lliamD/Vz'wZl 'NVENTOR' ATTORNEY Patented July 18, 1950 PROCESS FOR PRODUCING ARTIFICIAL FILAMENTS William D. Nicoll, Wilmington, Del., assignor to E. I. du Pont de Nemours & Company, Wilmington, Del., a corporation of Delaware Continuation of abandoned application Serial N 0.

477,720, March 2, 1943. This application January 28, 1949, Serial No. 73,323

19 Claims. (01. 1854) This invention relates to the production of crimped, wool-like filaments and fibers comprising regenerated cellulose and a protein.

This application is a continuation of my copending application Serial No. 477,720, filed March 2, 1943, now abandoned.

Many attempts have been made, heretofore; to produce a wool-like fiber or filament comprised of regenerated cellulose and a protein. Such fibers have great utility in producing mixed rayon-wool yarns and fabrics which can be dyed to substantially uniform color with wool dyes.

Crimped, regenerated cellulose-protein filamentsand fibers, as produced prior to this invention, have lacked one essential character of wool, namely, the ability to retain a substantial crimp after being subjected to a material stretch.

My co-pending application Serial No. 465,414, filed November 13, 1942, covers a process for the production of unique, permanently crimped woollike regenerated cellulose filaments and fibers. It has now been found that similar unique, permanently crimped regenerated cellulose-protein filaments and fibers can be produced in a similar manner.

It is therefore an object of this invention to produce new and unique, crimped regenerated cellulose-protein filaments and fibers which will retain a substantial crimp after being subjected to a material stretch, and which filaments and fibers have a high wet and dry tenacity.

It is still another object of this invention to produce regenerated cellulose-protein filaments and fibers which will crimp instantaneously upon being suspended, free from tension, in an aqueous Other objects of the invention will appear hereinafter.

Similar to my copending application above referred to, viscose-sulfuric acid-salt systems in which the minimum gel swelling factor of the regenerated cellulose filaments obtainable therefrom is less than 6.5 will hereinafterbe referred to as balanced viscose-sulfuric acid-salt spinning bath systems.

The gelswelling factor of regenerated 2621111- lose filaments is determined in the following manner:

A viscose of known composition is extruded through a spinneret into a sulfuric acid coagulating bath of known composition. The coagulated filaments, after leaving the bath, are wound in a single layer on to a bobbin with a helical wind of narrow pitch in such a manner that successive windings are very closely spaced. When the bobbin contains 2 to 6 grams of wet gel yarn, the bobbin is removed and rotated on a chuck to centrifuge off the bath carried with the filaments on to the bobbin. The acid-wet gel yarn is then cut from the bobbin and weighed. The whole operation should be carried out within The acid-wet gel yarn is washed and then dried to remove all the water therefrom 3:

four minutes.

and the dry yarn reweighed. The ratio of the Weight of acid-wet gel yarn to the weight of the dry yarn is termed its gel swelling factor.

concentration of sulfuric acid in the coagulating bath will result in the production of a regenerated cellulose having a high gel swelling factor.

If the acidity is gradually decreased (with the composition of the viscose and coagulating bath otherwise remaining the same), the gel swelling factor falls to a minimum and then rises again with a further decrease in the acidity. The gel swelling factor at the minimum will be termed the minimum gel swelling factor, and the acidity at this point will be termed the minimum gel swelling factor acidity.

The above objects can be accomplished, in general, by preparing a viscose composition containing 5% to 100% protein, based on the weightoi the cellulose in the viscose, and spinning filaments from said viscose composition in acoagulating and regenerating bath While observing the following highly critical combination of com ditions: Spinning filaments in a balanced viscose-sulfuric acid-salt spinning bath system in which the spinning bath contains zinc sulfate and the sulfuric acid content of the bath is between and of the minimum gel swelling factor acidity; imposing on said filaments, during the spinning thereof, a tension of at least 0.5'

gram per denier and a stretch of at least 40%;

and, after substantially complete regeneration of said filaments, relaxing the same completely free of all tension in a liquid which will swell the [By stretch of at least 40% is meant same.

a stretch (as measured between the point where the spun filaments are first converged in the bath, and collecting device) of at least 40%, based on its unstretched length] For practical purposes, it isgenerally desirable that the coagulating bath have a temperature of between 40 C. and 75 C. and preferably that the zinc sulfate content of the bath be from 0.1% to 3%.

The methods and means by which the present invention may be carried out will be apparent by reference to the following detailed description when taken in connection with the accompanying illustration, in which:

Figure 1 is a diagrammatic view, with parts shown in perspective, of one form of apparatus suitable for use in accordance with the present invention;

Figure 2 is a similar diagrammatic perspective view, with parts shown in perspective, of another modified form of apparatus for use in accordance with the present invention;

Figure 3 is a diagrammatic view of still another modified form of apparatus suitable for use in carrying out the present invention;

Figure- 4 is a typical gel swelling factor curve.

Referring to Figure 1, reference numeral ll designates a conduit line for a viscose-protein filament forming composition which is connected to any suitable source of supply. The conduit l l is connected in the usual manner to a candle filter l2, and the candle filter I2 is connected to a spinneret M by means of a goose-neck" I3. The viscose solution is extruded through the spinneret I 4' to form filaments 15. The bundle of filaments is passed about the convergence guide I6 and thence about roller guides l1 and take-off guide I8. From guide is the yarn is passed about a feed wheel l9 from which the yarn is fed through two vertically spaced sleeve guides 2| and 2-3. If desired, a liquid may be passed through the two sleeve guides by means of a nozzle 24. The liquidwill continuously force the yarn through the two sleeve guides. A rotatable cutter knife 25 may be positioned to rotate between the two sleeve guides 2i and 23, thereby cutting the yarn into small staple lengths. The cutter knife is mounted on a shaft 21 and is adapted to be rotated by means of a driven belt. The staple fibers 28 drop into a relaxing fluid 29 where they will be completely free from tension and will be substantially instantaneously crimped along the length thereof.

Referring to Figure 2 of the drawings, the yarn l5, after passing from the feedwheel I9, is led directly to a relaxing bath contained in container 2!, while completely freeing the yarn from tension. A short length of yarn is permitted to accumulate in the bottom of the container 2|. As soon as the yarn strikes the bath, it will be substantially instantaneously crimped as shown at 23. The yarn is continuously removed from the container 2 I by passing the same over rotatable guide 25 and wound on to a bobbin 3! which may be driven by surface drive roller 33. The yarn may be traversed on the bobbin in the conventional manner by means of a traverse guide 35. In passing between the bath and the bobbin, the yarn is dried by means of a forced draft drier 21. Just prior to winding the yarn on the bobbin 3 I, it may be slightly tensioned by means of pinch tensioning device 29.

Referring to Figure 3 of the drawings, the yarn l5, composed of freshly spun filaments, is passed from the s'pinneret M about fixed convergence guide 16, then through a long bath tank to a take-off guide IS. The yarn is then passed to draw-off rollers 3-0 and 32 which are of sufficient size to provide a surface area of sufficient extent to eliminate any material slippage of the yarn thereon. The yarn is thenpassed from draw-off roller 32 about guide roller 43, and then about stretching rollers 05 and 41. The yarn passes about rollers 45 and. 41 a number of times to eliminate any possibility of slippage of the yarn thereon. Between draw-off roller 32 and guide roller 53, the yarn is subjected to treatment with a stretching liquid 42, passed on to the yarn by means of conduit 00. The stretching liquid will be described with particularity hereinafter. The draw-off roller and stretching roller are positively driven to impart a portion of the tension and stretch on the yarn between the guide I 6 and the roller 30, and a portion between the roller 30* and the roller 45.

The apparatus shown in Figure 3 is particularly useful in such instances where the requisite tension. and stretch cannot be imposed on the filaments solely in their travel through the spinning bath. It has been found that when such filaments are passed into contact with a stretching bath, the requisite tension and stretch can be imposed on the yarn during the spinning thereof;

Figure 4 of the drawings discloses a typical gel swelling factor curve for a viscose of a given composition. From this curve, it will be noted that when the acidity of the bath in percentage by weight of sulfuric acid is 12%, the gel swelling factor of the yarn will be slightly under 9.0. When the acidity of the bath is reduced to 11%, the gel swelling factor lies between 5.0 and 6.0. When the acidity is further reduced to 10%, the gel swelling factor drops to between 3.0 and 4.0. With an acidity between 8% and 9%, the gel swelling factor has dropped to a minimum value of 3.0. Further reduction in the acidity of the coagulating bath will cause the gel swelling factor of the yarn to rise again in accordance with the contour of the curve shown in the drawing.

In its broad scope, the process of the present invention is operative and useful with any balanced viscose-sulfuric acid-salt spinning bath system. Particularly desirable crimped yarns and filaments will be obtained in accordance with the following specific combination of relationship factors:

(1) The viscose composition contains between 5% and 100% protein, based on the weight of cellulose content of the viscose.

(2) The viscose-protein composition has an alkali content of between 2% and 7%.

(3) The viscose-protein composition has a salt index of between 1.5 and 6.

4.) The coagulating and regenerating bath has a sulfuric acid content between 60 and 90% of that amount required to produce a yarn having a minimum gel swelling value.

(5) The coagulating and regenerating bath contains between 15% and 30% sodium' sulfate.

(6) The coagulating and regenerating bath contains between 0.5% and 3% zinc sulfate.

(7) The temperature of the coagulating and regenerating bath is between 40 C. and C.

(8) The temperature of the relaxing bath is sufficiently high to impart a shrinking action to the filaments at least equal to that of water at 20 C.

(9) Imposing on the filaments, during the spinning thereof, a tension of at least 0.5 gram per denier and a stretch of at least 40%, and after substantially complete regeneration of the filaments, relaxing the same completely free of all tension in a liquid which will swell the same;

The filaments travel a total length of at least inches in the regenerating andcoagu lating bath.

In addition to the above mentioned ingredicuts of the coagulating bath, it is permissible to have present as much as 6% or'7% glucose or i siinilar organic substances well known in the art.

The presence of glucose in the spinning bath is I not an essential feature of this process, but may" be desirable, particularly when continuous fi1ament yarn is produced. As a guide to the proportion of glucose to be used, it may be said that 2% of glucose can replace approximately 1% of g sodium sulfate.

In accordance with the above detailed process, the specific enumerated factors are all interdependent and must be adjusted in relation to one another in-order to obtain the desired resuit, 1. e. a satisfactory crimp.

It is, of course, understood that relaxing o f" the filaments in an aqueous medium completely free; of all tension is absolutely essential, no matter what variations may be introduced in the other conditions.

It is also essential that the tension on the filaments during the spinning (including stretching) be at least 0.5 gram per denier, and that a stretch of at least 40% be placed on the filaments. For each of the factors enumerated above, the range within which the process may be successfully operated has,

been indicated, but it will be apparent at once to one skilled in the art that if any one of the factors is set at or near the extreme lower or upper limit of its particular range, other factors may have to be adjusted in order to obtain the best results. To illustrate, if the acid content of the coagulating bath is near the lowest limit of the range, it is desirable to adjustsome of the other factors to restore the balance of the conditions, for example the zinc sulfate and sodium sulfate contents of the bath. Likewise, the bath temperature should desirably be raised.

Inthe case of a change in the alkali content of the viscose, I have found that the most impor tant other variable requiringadjustment is the acid content of the coagulating and regeneratQ ing bath. fAs' already stated, the acid content necessary to produce a good crimp should be between and 90 of the minimum g'elswell ing' acidity. I have found as an empirical rule that, over the operable ranges shown, a 1% increase in alkali content of the viscose is approxi mately compensated for by a 1 A;% increase in the acid content of the coagulating and regenfcrating bath.

above stated it is essential in accordance with this invention that a tension of at least 0.5 gram per denier and a stretch of at least fl0% be imposed on the filaments during the spinning thereof.

The tension and stretch imposed on the filament s may, of course,greatly exceed that {j above specified. Any tension or stretch under" that which will break the filaments may beused in accordance with the present invention. This tension and stretch must be imposed on the filaments during the coagulation and regeneration thereof when operating without a stretching bath as shown diagrammatically in Figure 1 of the drawings.

In some instances, however,-it may be impossible to impose that amount of stretch and tension without theuse of a stretching bath.

Under such circumstances, an arrangement as I showniin Figure 3 of the drawings maybe used.-

,sirable manner.

In the latter case, the requisite stretch and tension are partially imposed on the filaments dur- I ing the coagulation and regeneration thereof and partially imposed thereon during the stretching thereof. The path of the filaments through the coagulating and regenerating bath liquor must be sufiiciently long (at least 25 inches and prefera bly at least 50 inches) to substantially complete the regeneration thereof while in said bath. However, if the stretching bath is capable of regeneration due to heat or content of acid, the regeneration of the filaments may be completed in this bath. For the purposes of the present specification and claims, the spinning of the filaments shall include the passage of the filaments through the stretching bath. if a stretching bath is employed.

When a stretching bath is used in accordance with the present invention, it must follow thecoagulating bath and the yarn must be passed through the same with a continuation of tension and stretching begun in the coagulating bath. The degree to which the filaments are stretched or tensioned in the coagulating bath may be approximately the same as the degree to,

which they are stretched or tensioned in the stretching bath. Under some circumstances, it may be desirable to stretch and tension the filaments to a greater degree in the coagulating bath than in the stretching bath. Under other circumstances, it may be desirable to impose a greater degree of stretch and tension on the filaments in the stretching bath than in the coagulating bath. The stretching bath should preferably have a temperature of between about 50 0. and the boiling point thereof. The stretching bath should be composed of a non-alkaline, aqueous liquid preferably containing not to exceed that acidity equivalent to 3% of surfuric acid. This) bath is preferably composed of water.

The relaxing bath may be composed of any liquid which is capable of swelling the celluloseprotein filaments. substantially regenerated by the. time they are subjected to relaxation in the relaxing bath, the

latter will'have substantially no regenerating action on the filaments. The relaxing bath preferably comprises water and. it may be acidic, neutral, or slightly alkaline. The relaxing bath may contain an acid or a salt such as calcium chloride, sodium thiocyanate, calcium thiocyanate or the like. Such salts will often impart a particularly desirable swelling action to the filaments, where i by crimping takes place in a particularly desimilarly to the above mentioned salts, also have a desirable swelling action on the filaments; but

the concentration of such alkaline agents should be low (not over 0.5%) because stronger al'-" kaline solutions may have detrimental effects on the strength of cellulose-protein fibers. The temperature of the relaxing bath may vary widelyas this is not critical. The relaxing bath may comprise or consist of organic liquids such as glycerol if the latter is used at a temperature of the order of (1., at which temperature glycerol is found to swell regenerated cellulose filaments. Regenerated cellulose-protein filaments may be relaxed in a bath consisting of anhydrous liquid ammonia since the latter is capable of swelling cellulose. The relaxing bath may contain a hardening agent for the protein, for example formal-:

Since the filaments will be Such relaxing baths may also contain purification agents such as sodium car bonate, caustic soda and the like, which may,

dehyde. Whatever the composition and temperature of the relaxing bath may be, the filaments must be allowed to rest in the relaxing bath free of all tension. The filaments may be passed directly to the relaxing bath from the stretching bath in the form of continuous filaments or staple fibers. Alternatively, the filaments passing from the stretching bath may be collected in any desired manner, for example on a bobbin in accordance with the bobbin spinning process, in a bucket cake in accordance with the bucket spinning process, or loosely in a container therefor. The product may be washed acid free, desulfured and/or bleached prior to the time it is immersed in the relaxing bath or it may be relaxed while in the acid state and then washed, desulfured and/or bleached after crimping has been accomplished.

As above set forth, it is essential that the filaments be completely relaxed so that they are free toshrink to the maximum extent. Probably the best method of securing such complete relaxation is to immerse the skeins or staple in the relaxing bath, making sure that there is ample room for the fibers to crimp freely and shrink. If the filaments are not free from all tension, as for example when they are allowed to relax only partially in a wash and bleach machine by hanging skeins on a rod under the weight of a large amount of liquid, the results are found to be unsatisfactory. This time of immersion of the filaments in the relaxing bath is not critical. Under the proper conditions of relaxation, the crimp will be formed in the fibers in the relaxing bath practically instantaneously. It was considered unexpected and surprising that yarns spun under the above described conditions would develop crimp on relaxing in a, swelling medium after the yarn had been subjected to washing treatments and other purification treatments, and even after the yarn had been dried prior to relaxation.

The following examples disclose the use of casein and soy bean protein. However, it is possible to use any alkali soluble protein in accordance with the present invention. For example, crimped yarns have ben prepared from viscose modified with (based on the weight of the cellulose) of a reduced and regenerated wool obtained by treating natural wool with thioglycolic acid to break down the disulfide linkages, dissolving in alkali and reprecipitating with acid. Among other proteins which may be used may be mentioned albumin, leucosin, the globulins, zein, gliadin, etc. The amount of protein material added to the viscose may vary between 5% and 100% of the weight of the cellulose in the viscose. It is not necessary that the viscose illustrate in detail specific steps by which the" present invention may be carried out.

Example I through a multiple hole 010-00035") spinneret into an acid-salt coagulating and regeneratingbath containing 8.5% H2304, 19% NazSOa, 4%

glucose and 0.85% ZnSO4. The thread formed is carried around a series of floating guides located in the bath to impart tension thereto and. is then taken up on a bobbin rotating at a peripheralspeed of approximately 3,500 inches per minute.

The total travel of the filaments is approximately 180 and the maximum tension on the thread at the point where it is wound up on the bobbin is approximately 80 grams or 0.53 gram per denier thread. The gel yarn, after collection on the bobbin, is washed free of acid and dried under tension on the bobbin. To produce crimped fibers, it is only necessary then to form the straight thread into skeins and to suspend the skeins free from tension in a bath of hot water (at least C.) or hot dilute (0.3%) solution of sodium carbonate. this manner after drying have a wool-like appearance and hand, and if the crimps are removed by stretching, they can be restored by again suspending the skein in hot water free from tension.

These fibers can be dyed alone or in mixture with wool using acid or wool type dyes. They also may be dyed with direct or cotton dyes.

Example II Viscose modified by the addition of 15% casein (based on the weight of the cellulose in the viscose) in a manner similar to that described in Example I is spun at a salt index of 4.4 into a bath containing 9% H2504, 23% NazSO4, 4% glucose and 0.85% 211804. The general procedure used in spinning is the same as that of Example I, except that the final tension in this case is 0.7 gram per denier on the gel filaments. After spinning, the yarn is washed and out into staples approximatly 2 inches in length and the staples are suspended free from tension in a bath of hot Water having a temperature of 80 C. On entering the bath of .hot water, these filaments crimp strongly and the crimps so produced are relatively permanent in the sense that, if removed be made first and later modified with the protein since it is possible to add the protein to the cellulose xanthate at the time the viscose dispersion is initially prepared. However, due to the degradative effects of alkali on proteins, it is generally more satisfactory to dissolve the protein in a previously prepared viscose and, thereafter, to spin the resulting mixture as soon as possible. The most efficient method for dissolving a protein, for example casein, in viscose, is to first moisten the protein with water or an aqueous alkaline solution, allow the protein to swell and then to add the swollen protein to the viscose. Under these conditions, the protein dissolves readily in the viscose and only a few minutes stirring are required to obtain a smooth, even dispersion.

The following examples which are not to be considered limitative of the present invention,

by stretching, they may be restored by again immersing the fibers, free from tension, inwater having a temperature of 60 C. These fibers, like those of Example I, may be dyed with either wool or cotton dyes and may be used either alone or for blending purposes with a wide variety of I other staple fibers.

Example III Crimped fibers obtained in in a 1% solution or formaldehyde 'to harden or insolubilize the protein. Thethread is then relaxed in a bath of water having; atemperature of 80 'C. with the production ofhighlycrirnped fibers which are wool-likein hand and may be dyed with acid or wool dyes.

Emample t I Viscose having a normalcomposition of 7% oellulose and6% alkali ismodified by the addition of an amount of caseinfequivalent to the cellulose contained in the original-solution." To

make this addition, 105 parts'of casein are moistened with 495 parts of' water and; after being allowed to stand for a few minutes to permit" thorough wetting ofthe casein,'there are added to it 1,500 parts of viscose. The mixture is then stirred until a smooth uniform dispersion is obtained. The composition ofthis-mixtureis approximately cellulose, 5% casein and 4.3%

total alkali. The mixed solution is extruded through a multiple hole spinneret intoan acidsalt bath containing 5.35% IIzSO4,"23% N-a2SO4, 4% glucose and 0.85% ZnSO4. The bath travel is 180 inches and the maximum tension on the? protein hardening bath comprising 7.6% sodium chloride, 3.9% aluminum sulfate, and 3.3% formaldehyde. A special feature of this process is that the hardenin bath serves the dual purpose of a relaxing bath producing crimps in the fibers at the same time that these fibers are toughened and rendered insoluble.- The time'reqdired for completing the hardeningtrea'tmentis about 24 hours after which the product is-wash ed-treated with afinish-and dried. The resulting fibers are wool-like and dye deeply withmost types of wool 'dyes. They also possess a pleasant, soft-hand.

. l m H Viscose containing 7% celluloseand' 6% alkali is modified by the additiorr 'of an amount otcasein equivalent to the cellulose content of the viscose; the casein in this casebeing added in the form of asolution inalkali. The mixed solution then contains 5% cellulose, 5% casein and 6% alkali. In addition, there is added'to the solution 0.25% of a styrene/maleic anhydride interpolymer which has the property of functioning as fa protein hardening agent. The bathcompo sition used for spinning contains ,8.1.% H2SO4, 23% Na2SO4, 4% glucose and0.85% ZnSO i. The spinneret used containsbO holes of 0.0035" diameter each. The bath travel is-12 0", the bath temperature 55 C., the thread speed at'the bobbin 3500"/min. and the tension on the thread at the bobbin approximately'OA g./d. 'After spinning the thread is cut into staples and relaxed completely in water having a temperature of ill" C. The resulting fibersar'e highly crimped and the crimps are permanent in the sense that, if temporarily removed by stretching they may again be recovered by suspending thefibers in a liquid swelling bath free from tension. R

. Example V1 p t i i Viscose, 7% cellulose and 6% alkali, is modified bythe addition of 33%caisein and 2.5% of a 'styrene/maleic anhyclride interpolmer (both based on the cellulose contained in the viscose), Sufilcient alkali is also addedf tofl maintainthe original alkalinity of the viscose and'the resultant form of staple or of continuous filaments. be readily demonstrated by manually stretching,

, and crimps to give the original structure.

surprising property is, of course, of greatimporl0 spinningsolution which contains 6% cellulose, 2% casein, 0.25% styrene/maleic anhydride interpolymer and 6% total alkali is spun into filaments in a manner similar to that described in Example V except that the bath used contains 7% sulfuric acid, 23% NazSO4, 4% glucose and 0.85% ZnSOr. Maximum tension on the thread at the bobbin in this case is approximatelyOfi g./d. and after spinning the gel thread is cut intostaple lengths without intermediate wash- 'ings and the staples are permitted to relax completely in hot (BO- C.) water.

The staples obtained are finely crimped, can be dyed with acid dyes and have a pleasant wool-like hand.

The crimped filaments and fibers produced by the process of the present invention are entirely new and different in character from any previously known crimped regenerated celluloseprotein filaments or fibers. They are characterized by unique and outstanding propertiesnot found in the crimped fibers produced heretofore.

One of these entirely new and unexpected properties 'lies in the fact that the crimp, after being removed through stretching, combing, or other "mechanical treatment, is substantially completely restored to the fiber simply by suspending it in water, or other aqueous liquid, in the absence of tension. The crimp regain is practically instantaneous, whether the fiber treated be in the It can or repeatedly combing a somple of crimped fiber so as-to destroy its crimp, then immersing the sample in Water, whereupon it at once crinkles This tance in the industrial processes to whichthe fibers may be subjected. For example, carding usually destroys, at least partly, the crimp in an ordinary crimped fiber. Fibers made by this process, however, may be'carded and afterward immersed in water, whereby the original crimp is restored completely or substantially'so. No pr'e viously known crimped re fii erated cellulose? protein fibers even remotely possess this remarkable characteristic. 3 ,"f

It istheorized that the production of crimped high tenacity'fibers accordingto this invention is possible primarily by reason of the fact that during spinning there is formed" in individual filaments a certain kind of non-uniformity ith respect to the'prientation of the cellulosetcorn prising the edges or outside boundary of the filament as compared with-that comprising the interior sections of the filament. When fibers possessing such non-uniformity in their cross sec;- tions are permitted to shrink freely, the different layers of regenerated cellulose do not shrink to thesame extent andthe fibers tend spontaneously to fold over and produce a crimped efiectLfFo'r this reason, use is made of thehigh spinning tjensions which are a fundamentalfeature of the present invention. 'A proper balance between the above described relationship factors is considered to be essential since only under such selected conditions is the rate ofpenetration 'of acid into the thread such that a good differentia+ tion can be obtained between the degree oi"; orientation of fiber wall and fiber core. There is a possibility that differences in the fiber structure (density and degree oforientation) occur across the filament which ultimately cause the fiber to crimp when relaxed. The foregoing theoretical discussion is not, however, to be con strued as limiting the process of this invention.

The high tenacity crimped fibers which may be obtained as a result of the present invention are characterized by filament strength of from 2.25 ever 3 grams per denier dry tenacity, and from 1,25 to over 2 grams per denier wet tenacity. The dry extensibilities, after straightening the crimp therefrom, for threads formed in accordance with the present invention are of the order of to 20%, depending on the spinning tension used in their formation, and in general, it can be said that the extensibilities of crimped fibers produced in accordance with the present invention are better than those of straight fibers of equal tensile strength but spun without permitting free shrinkage. The curly crimp in the fibers produced in accordance with the present invention is durable and produces a pleasing, wool-like appearance and hand. In the case of fibers which have been cut to staple length before being permitted to relax in water, the crimps obtained are quite irregular, both as to their number per inch and their arrangement around the fiber axis. It is difficult, therefore, to define the degree of crimp obtained in these fibers in a quantitative manner, but in general, it may be said that the number of crimps per unit length along the axis of the unstretched fiber is above 10 crimps per inch. This means that these fibers are easily distinguishable from ordinary regenerated cellulose staple fibers, or any previously known regenerated cellulose-protein fibers, even those made by the so-called acid-cutting process, sinceat most the latter do not show more than 5 or 6 crimps per inch. The crimps in the fibers are remarkably resistant to laundering with soap. As has been mentioned previously, even after removing the crimp by" stretching the filaments, the crimp can be restored by subjecting the filaments or fibers to another relaxing treatment in a liquid.

, Continuous filament yarn comprising crimped filaments of the type hereinabove described is particularly desirable for the production of woven and knit goods where more than average yarn strength, together with, a wool-like hand, is desired. The crimped staple fibers of the present invention are very desirable for the production of a unique and superior spun yarn. Fabrics produced from both continuous filament and spun yarn made in accordance with the present invention will have a very desirable hand, due to regain of filament and fiber crimp upon wetting.

Since it is obvious that many changes and modifications can be made in the above described details without departing from the nature and spirit of the invention, itis to be understood that the invention is not to be limited to the said details except as set forth in the appended claims.

I claim:

v 1. A process for the production of crimped regenerated cellulose-protein filaments and fibers which comprises the steps of spinning filaments from a viscose solution containing from 5% to 100% protein, based on the weight of the cellulose in the viscose, into a coagulating and regenerati'n'g bath and then, after regeneration is sub- 'stantially complete, relaxing the same completely :free from all tension in a liquid which will swell the same, said steps being carried out in accordance with the following relationship factors: -(1) The viscose-protein composition has an alkali content of between 2% and 7%; (2) The viscose-protein composition has a salt index of between 1.5and 6; (3) The coagulating and regenerating bath has a sulfuric acid content between about 5.35% and 9.00% and between 60% and of the minimum gel swelling factor acidity; (4) The coagulating and regenerating bath contains between 15% and 30% sodium sulfate; (5) The coagulating and regenerating bath contains between 0.5 92- and 3% zinc sulfate; (6) The temperature of the coagulating and regenerating bath is between 40 C. and 75 0.; ('7) The temperature of the relaxing bath is sufficiently high to impart a shrink-ing action to the filaments at least equal to that of water at 20 C. (8) Imposing on the filaments during the spinning thereof a tension of at least 0.5 gram per denier and a stretch of at least 40%; (9) The filaments travel a total length of at least 25 inches in the regenerating and coagulating bath.

2. A process as defined in claim 1 in which said filaments are passed,- inthe spinning thereof, through a non-alkaline stretching bath containing not to exceed that acidity equivalent to 3% sulfuric acid.

3. A process as defined in claim 1 in which said filaments are passed, in the spinning thereof, through a non-alkaline stretching bath containing not to exceed that acidity equivalent to 3% sulfuric acid and having a temperature between 50 C. and the boiling. point thereof.

4. A process as defined in claim 1 in which said filaments are passed, in the spinning thereof, through a stretching bath composed essentially of water having a temperature between 50 C. and the boiling point thereof.

5. A process as defined in claim 1 in which said filaments are passed, in the spinning thereof, through a non-alkaline stretching bath containing not to exceed that acidity equivalent to 3% sulfuric acid and in which at least a portion of said tension and stretch is imposed on the filaments in the spinning bath and a portion of said tension and stretch is imposed on the filaments in the stretching bath.

6. A process as defined in claim 1 in which said relaxing liquid is water.

7. A process as defined in claim 1 in which said filaments are passed, in the spinning thereof, through a non-alkaline stretching bath containing not to exceed that acidity equivalent to 3% sulfuric acid and in which said relaxing liquid is water.

8. A process as defined in claim 1 in which said filaments are passed, in the spinning thereof, through a non-alkaline stretching bath containing not to exceed that acidity equivalent to 3% sulfuric acid and having a temperature between 50 C. and the boiling point thereof and in which said relaxing liquid is water.

9. A process as defined in claim 1 in which said filaments are passed, in the spinning thereof, through a stretching bath composed essentially of water having a temperature between 50 C. and the boiling point thereof and in which said relaxing liquid is water.

10. A process as defined in claim 1 in which said filaments are passed, in the spinning thereof, through a non-alkaline stretching bath containing not to exceed that acidity equivalent to 3% sulfuric acid and in which at least a portion of said tension and stretch is imposed on the filaments in the spinning bath and a portion of said tension and stretch is imposed on the filaments in the stretching bath and in which said relaxing liquid is water.

'11. A process as defined in claim 1 in which the filaments are relaxed in the relaxing bath immediately after stretching the same.

12. A process as defined in claim 1 in which the filaments are collected on a yarn support and subjected to a washing treatment after stretching and prior to relaxing.

13. A process as defined in claim 1 in which the filaments are collected on a yarn support and subjected to a washing and drying treatment after stretching and prior to relaxing.

14. A process for the production of crimped regenerated cellulose-protein filaments and fibers which comprises the steps of spinning filaments from a viscose solution containing from to 100% protein, based on the weight of the cellulose in the viscose, into a coagulating and regenerating bath and then, after regeneration is substantially complete, freely suspending the filaments in filamentous structure form in an aqueous liquid bath having a strong shrinking action on the filaments and in complete absence of tension, to completely relax the same, said steps being carried out in accordance with the following relationshi factors: (1) The viscoseprotein composition has an alkali content of between 2% and 7%; composition has a salt index of between 1.5 and 6; (3) The coagulating and regenerating bath has a sulfuric acid content between 5.35% and 9.00% and between 60% and 90% of the minimum gel swelling factor acidity; (4) The coagulating and regenerating bath contains between and 30% sodium sulfate; (5) The coagulating and regenerating bath contains between 0.5% and 3% zinc sulfate; (6) The temperature of the coagulating and regenerating bath is between 40 C. and 75 C.; ('7) The tem perature of the relaxing bath is sufficiently high to impart a shrinking action to the filaments at least equal to that of water at C.; (8) Imposing on the filaments during the spinning thereof a tension of at least 0.5 gram per denier and a stretch of at least 40%; (9) The filaments travel a total length of at least inches in the regenerating and coagulating bath.

15. A process as defined in claim 14 in which the relaxing treatment liquid is water having a temperature of at least 20 C.

16 A process as defined in claim 14 in which the filaments are stretched in a secondary bath comprising water having a temperature of at least 60 C.

17. A process as defined in claim 14 in which the filaments are subjected to a washing treatment after regeneration and prior to said relaxing treatment.

18. A process as defined in claim 14 in which the filaments are subjected to a washing treat- (2) The viscose-protein ment and dried after regeneration and prior to said relaxing treatment.

13. A process as defined in claim 14 in which the relaxing bath comprises a dilute solution of formaldehyde.

WILLIAM D. NICOLL.

No references cited.

Certificate of Correction Patent No. 2,515,889 July 18, 1950 WILLIAM D. NICOLL It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows:

Column 8, line 25, before the Word thread insert for 150 denier; column 10,

line 32, for somple read sample; column 14, line 28, for the claim number 18 read 19;

and that the said Letters Patent should be read as corrected above, so that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 17th day of October, A. D. 1950.

THOMAS F. MURPHY,

Assistant Commissioner of Patents. 

1. A PROCESS FOR THE PRODUCTION OF CRIMPED REGENERATED CELLULOSE-PROTEIN FILAMENTS AND FIBERS WHICH COMPRISES THE STEPS OF SPINNING FILAMENTS FROM A VISCOSE SOLUTION CONTAINING FROM 5% TO 100% PROTEIN, BASED ON THE WEIGHT OF THE CELLULOSE IN THE VISCOSE, INTO A COAGULATING AND REGENERATING BATH AND THEN, AFTER REGENERATION IS SUBSTANTIALLY COMPLETE, RELAXING THE SAME COMPLETELY FREE FROM ALL TENSION IN A LIQUID WHICH WILL SWELL THE SAME, SAID STEPS BEING CARRIED OUT IN ACCORDANCE WITH THE FOLLOWING RELATIONSHIP FACTORS: (1) THE VISCOSE-PROTEIN COMPOSITION HAS AN ALKALI CONTENT OF BETWEEN 2% AND 7%; (2) THE VISCOSE-PROTEIN COMPOSITION HAS A SALT INDEX OF BETWEEN 1.5 AND 6; (3) THE COAGULATING AND REGENERATING BATH HAS A SULFURIC ACID CONTENT BETWEEN ABOUT 5.35% AND 9.00% AND BETWEEN 60% AND 90% OF THE MINIMUM GEL SWELLING FACTOR ACIDITY; (4) THE COAGULATING AND REGENERATING BATH CONTAINS BETWEEN 15% AND 30% SODIUM SULFATE; (5) THE COAGULATING AND REGENERATING BATH CONTAINS BETWEEN 0.5% AND 3% ZINC SULFATE; (6) THE TEMPERATURE OF THE COAGULATING AND REGENERATING BATH IS BETWEEN 40*C. AND 75*C.; (7) THE TEMPERATURE OF THE RELAXING BATH IS SUFFICIENTLY HIGH TO INPART A SHRINKING ACTION TO THE FILAMENTS AT LEAST EQUAL TO THAT OF WATER AT 20*C.; (8) IMPOSING ON THE FILAMENTS DURING THE SPINNING THEREOF A TENSION OF AT LEAST 0.5 GRAM PER DENIER AND A STRETCH OF AT LEAST 40%; (9) THE FILAMENTS TRAVEL A TOTAL LENGTH OF AT LEAST 25 INCHES IN THE REGENERATING AND COAGULATING BATH. 